Obtaining micro- and macro-rock properties with a calibrated rock deformation simulation

ABSTRACT

A method for estimating a property of an earth formation includes: obtaining a sample of rock; scanning the sample to determine internal rock damage; measuring a deformation parameter of the sample; constructing a mathematical model of the sample that replicates the determined and measured internal rock damage distribution; simulating the one or more tests using the mathematical model; obtaining a rock deformation parameter using the one or more simulated tests corresponding to the measured rock deformation parameter; comparing the rock deformation parameter obtained from the one or more simulated tests to the corresponding measured rock deformation parameter; adjusting parameters of the mathematical model based upon the rock parameter obtained from simulation not being within a selected range of the measured rock parameter; and providing the mathematical model as a verified mathematical model based upon the rock parameter obtained from simulation being within a selected range of the measured rock parameter.

BACKGROUND

Earth formations may be used for various purposes such as hydrocarbonproduction, geothermal production, and carbon dioxide sequestration. Inorder to efficiently employ resources for using an earth formation, itis necessary to know one or more properties or parameters of the earthformation. One example of a property is unconfined compressive strength(UCS). By knowing the UCS of formation rock, a production engineer forexample can determine how fast to pump hydrocarbons from a well withoutproducing sand grains. Many types of other actions may also be performedby knowing the properties of formation rock. Therefore, it would be wellreceived in drilling and production industries if techniques weredeveloped to accurately and efficiently estimate properties of earthformations.

BRIEF SUMMARY

Disclosed is a method for estimating a property of an earth formation.The method includes: obtaining a sample of rock from the earthformation; scanning the sample with a volumetric imaging device toobtain a three-dimensional volume representation of the sample;determining internal rock damage of the sample using thethree-dimensional volume representation of the sample; performing one ormore tests on the sample using a rock test device; measuring adeformation parameter of the sample using a deformation sensor;constructing a mathematical model of the sample that replicates thedetermined and measured internal rock damage and damage distribution ofthe sample; simulating the one or more tests using the mathematicalmodel; obtaining a rock deformation parameter using the one or moresimulated tests corresponding to the measured rock deformationparameter; comparing the rock deformation parameter obtained from theone or more simulated tests to the corresponding measured rockdeformation parameter; adjusting parameters of the mathematical modelbased upon the rock parameter obtained from simulation not being withina selected range of the measured rock parameter; and providing themathematical model as a verified mathematical model based upon the rockparameter obtained from simulation being within a selected range of themeasured rock parameter; wherein the determining, constructing,obtaining a rock deformation parameter, comparing adjusting, andproviding are performed using a processor.

Also disclosed is a system for estimating a property of an earthformation. The system includes: a volumetric imaging device configuredto scan a sample of rock form the earth formation to obtain athree-dimensional volume representation of the sample; a rock testdevice configured to perform one or more tests on the sample; adeformation sensor configured to measure deformation of the sample dueto the one or more tests; a memory having computer-readableinstructions; and a processor for executing the computer-readableinstructions. The computer-readable instructions include: determininginternal rock damage of the sample using the three-dimensional volumerepresentation of the sample; constructing a mathematical model of thesample that replicates the determined internal rock damage and damagedistribution of the sample; simulating the one or more tests using themathematical model; obtaining a rock deformation parameter using the oneor more simulated tests corresponding to the measured rock deformationparameter; comparing the rock deformation parameter obtained from theone or more simulated tests to the corresponding measured rockdeformation parameter; adjusting parameters of the mathematical modelbased upon the rock parameter obtained from simulation not being with aselected range of the measured rock parameter; and providing themathematical model as a verified mathematical model based upon the rockparameter obtained from simulation being within a selected range of themeasured rock parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a flow chart for a method for estimating a property of rock inan earth formation;

FIG. 2 depicts aspects of a volumetric imaging device for scanning thecore sample to determine internal damage to the rock of the core sample;

FIG. 3 depicts aspects of a rock test device;

FIG. 4 depicts aspects of production equipment; and

FIG. 5 depicts aspects of drilling equipment.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method presented herein by way of exemplification and notlimitation with reference to the figures.

Disclosed are methods and apparatus for estimating a property of anearth formation. The methods and apparatus involve simulating formationrock features using a mathematical model of the rock features andcalibrating the model using tests of actual samples of the rock.Accurate property values are thus estimated from an accurate rock model.In addition, drilling and/or production actions may be performed on theformation based upon knowledge of the estimated property.

It is noted that testing of rock samples alone may not be sufficient toprovide the desired accuracy of estimated property values. Thecollection of rock parameters from rock tests can be biased due todifferent reasons. One reason is the rock sampling itself. Commonpractice involves collecting rock cores e.g. from a wellbore. With thisprocedure only certain sections of the wellbore may be sampled producinga subset of sample data. From the rock core further subsets aregenerally created called “plugs”. In some cases the plugs are directlycollected from the wellbore wall.

On the plugs the rock tests are carried out. The selection of the plugsas samples is based on a variety of decisions which are not discussed indetail here. Important to note however, is that the heterogeneity of therock column may not be fully represented as the material properties, thecoherency or degree of damage (e.g., micro-cracks) may differ from onelocation to another thus making the plug not fully representative of theearth formation.

The second source of bias may be introduced by the rock teststhemselves. Multi-stage rock tests for example are carried out tomeasure rock stress/strain curves under increasing stress conditions. Inthese tests the sample is loaded and unloaded repeatedly. In each cycle,deformation is halted before significant inelastic behavior occurs toavoid rock failure that may fully destroy the sample. A destroyed samplewould make further measurements impossible. All of these loading cycleshowever introduce damage to the rock material by crack closing as wellas the creation of micro cracks which are linked to the onset ofinelastic behavior. Because of this cumulative damage the rockmechanical properties of the sample may change throughout the test andintroduce bias.

Apart from these multistage tests, other tests (e.g. unconfinedcompressive strength measurements) that provide useful information mayrequire the full destruction of the sample during the test procedure,thus, not allowing any other subsequent tests on the same plug.

The main shortcomings testing alone are in summary (a) the lack of fullyrepresenting the rock's variability to due to the sampling and (b) theintroduction of damage into the sample during the testing up to when itsdestruction inhibits further rock tests.

To overcome these shortcomings and provide other advantages, the methodsand apparatus disclosed herein link the physical rock tests to asimulation of the very same tests or type of tests. The simulation isbased on a mathematical material model of the formation rock that hasthe capability to track and quantify the damage history and damagedirectionality of the material. This model may be referred to herein asa “micro-crack evolution model.” In one or more embodiments, the modelis based on a modified Mohr-Coulomb model having a term representingdilatation in an out-of-plane (i.e., out of fracture plane) orientation.U.S. patent application Ser. No. 15/006,281 entitled “Mechanisms-BasedFracture Model For Geomaterials” discloses an example of themathematical material model and is incorporated by reference in itsentirety.

Based on the geometry and property distribution of the physical sample,a digital model (i.e., a mathematical model that is implemented by aprocessor such as in a computer processing system) is created. Thedigital model is calibrated against a non-destructive test or a test inwhich the physical sample is damaged incrementally (e.g. multi-stagetest). Model validation is achieved if the parameters of the digitalrock model adequately represent the rock deformation parameters of thephysical sample. For example, model validation may be achieved if theresults of a simulated multi-stage test are the same as the results ofan actual multi-stage test for each incremental test.

The verified digital model can then be used to forward model multipledestructive tests. Furthermore, the model is able to separate themicro-properties of the rock matrix as well as the bulk macro-propertiesof the rock as a result of its internal damage. The model's ability toadd a variable degree and distribution of damage to the model allowscreation of a rock property catalogue with respect to verifying degreesof damage.

In general, the term “macro-property” relates to a property that isvisible to the naked eye, while the term “micro-property” relates to aproperty that is not readily visible to the naked eye. With respect toeach other, macro-properties are physically larger thanmicro-properties. It can be appreciated that properties may be sampledependent and/or scale dependent (i.e., dependent on physical size ofthe sample). Hence, micro-properties may be differentiated frommacro-properties.

FIG. 1 is a flow chart for a method 100 for estimating a property of anearth formation. Block 101 calls for obtaining a sample of rock from theearth formation. The sample may be a sidewall core sample or a coresample of rock being drilled to drill a borehole. In one or moreembodiments, a plurality of plugs may be extracted from one core sample.The physical sample may be referred to hereafter as a “plug” but mayalso represent another form of rock or material sample. The sample maybe extracted from a formation using a coring tool such as illustrated inFIG. 4.

Block 102 calls for scanning the sample with a volumetric imaging deviceto obtain a three-dimensional volume representation of the sample. Thevolumetric characteristics (such as voids, macro-cracks or micro-cracks)of the sample or plug are captured with the volumetric imaging device(e.g. computer tomography). The volumetric imaging device in one or moreembodiments captures the radiological density of the plug and storesthis information as a volumetric data set. FIG. 2 depicts aspects of oneexample of a volumetric imaging device 20. The volumetric imaging device20 includes an energy emitter 21 configured to emit energy into a sample22 of the rock of the earth formation. The volumetric imaging device orscanner 20 also includes an imager 23 configured to receive energy fromthe sample 22 due to interaction of the emitted energy with the sample22 and to provide a three-dimensional image of the sample 22 using thereceived energy. A processor 24 may process data received from theimager in order to provide the three-dimensional image. Non-limitingembodiments of the energy emitted by the scanner 20 include X-rays.Other types of energy may also be used. In one or more embodiments, thevolumetric imaging device is a computed tomography (CT) scanner ormico-CT scanner.

Block 103 calls for determining internal rock damage of the sample witha processor using the three-dimensional volume representation of thesample. The volumetric data is used to derive a representative,statistical and/or discrete data set on matrix material of the samplethat quantifies void, micro-crack, and macro-crack distribution in theplug.

Block 104 calls for performing one or more tests on the sample using arock test device. The one or more tests may include non-destructive rocktests and/or destructive rock tests that cause rock damage such as amulti-stage rock test. In this block, the plug is subjected to one ormore rock tests which may include subjecting the sample to a force inorder to capture rock parameters. These may be tests which, ideally, arenon-destructive and do not introduce significant damage to the material.The non-destructive and/or destructive tests may include measuring adeformation parameter of the material when a force is applied to theplug. Single-stage rock tests and/or multistage stage rock tests tocapture the stress/strain behavior may be carried out next. Thiscomplements the rock property catalogue but is expected to introducedamage to the plug. FIG. 3 depicts aspects of a rock test device 30. Therock test device 30 may include a force generator 31 such as a pistonfor applying a force to the sample 22 and a sensor 32 for sensing acorresponding change of the sample 22 due to the applied force.Non-limiting embodiments of the sensor 32 include a strain sensor 33, asize measuring sensor 34 and an acoustic microphone or transducer 35. Aprocessor 36 may process data received from the sensors to provide arock deformation measurement.

Block 105 calls for measuring a rock deformation parameter of the sampleusing a sensor. The terms “deformation” or “damage” relate to physicalchanges to a rock that results from one or more forces applied to therock. Non-limiting embodiments of the deformation parameter include astress curve, a strain curve, and/or locations in the sample of stressand/or strain. Physical deformation such as strain may be measured withthe strain sensor 33 coupled to the sample 22. External damage may besensed by the size measuring sensor 34 configured to sense the size ofthe sample it undergoes an applied force. The internal damage of theplug may be monitored by measuring the acoustic emissions related tomicro-cracking. That is, as a test force is imposed on the sample, theacoustic transducer 35 (or multiple transducers) receives acousticenergy (e.g., sound waves) related to the deformation or cracking of thesample. Using triangulation or other techniques, a location of a sourceof the acoustic energy (i.e., location of the deformation or cracking)can be determined. Also a repeated volumetric imaging andcharacterization run can provide supporting information on the degreeand the distribution of internal damage. The data sets are to be usedfor verification purposes discussed in block 109 further below. The rockparameters obtained for the plug represent the bulk properties and arereferred to hereafter as the physical “macro-properties”.

Block 106 calls for constructing a mathematical model of the sample thatreplicates the determined internal rock damage and damage distributionof the sample. In one or more embodiments, the mathematical model is adigital three-dimensional model that is configured to be implemented bya processor such as in a computer processing system. In otherembodiments, the model may have less than or greater than threedimensions. The model is also configured to model the evolution ofmicro-cracks and macro-cracks as the cracks develop due to appliedforces. From the volumetric characterization of the plug, a digitalrepresentation is built for the purpose of a digital mechanicalsimulation. The representative, statistical and/or discrete distributionof matrix material, void space and damage (e.g. micro cracks) of theplug are represented in the digital model to replicate the plug'sinternal structure and damage. As noted above, one example of thedigital model is a mechanism-based material model such as the modifiedMohr-Coulomb model having a term representing dilatation in anout-of-plane orientation.

Block 107 calls for simulating the one or more tests using themathematical model. The digital model is populated with plug'smacro-properties derived from the physical tests carried out on theplug. The performed rock tests are simulated with the digital model ofthe plug using the mechanism-based material model capable of trackingthe damage history and damage directionality. The parameters of thedigital rock tests are collected. These may include the overall bulkcharacteristics of the test such as stress and/or strain curves andacoustic properties as well as discrete characteristics such as strainlocalization patterns, internal damage and/or acoustic emissions.

Block 108 calls for obtaining a rock deformation parameter using the oneor more simulated tests corresponding to the measured rock deformationparameter.

Block 109 calls for comparing the rock deformation parameter obtainedfrom the one or more simulated tests to the corresponding measured rockdeformation parameter. The results of the physical rock tests with bulkparameters and—upon availability—discrete observations (e.g. acousticemissions, introduced physical damage as revealed by volumetric imagingetc.) are compared with the outcome of the digital simulation todetermine if the outcome of the digital simulation matches the resultsof the one or more physical rock tests. The term “match” relates todetermining if the outcome of the digital simulation is within aselected range, such as within 5% deviation for example, of the outcomeof the physical rock tests. If several tests of the same type areperformed, the range may be selected to provide a 95% confidenceinterval. The selected range in general will be determined by an amountof desired accuracy of the digital model.

Block 110 calls for adjusting one or more parameters of the mathematicalmodel based upon the rock parameter obtained from simulation not beingwith a selected range of the measured rock parameter. If the bulkproperties returned from the mathematical model simulation are differentfrom those of the plug or if the discrete observations are different,then the mathematical model properties are adjusted. This will apply tothe mathematical model's matrix properties, which are updated and thesimulation is re-run until a match is achieved. The mathematical modelcan be calibrated with one or more parameters to predict materialbehavior that is consistent with experimentally observed materialbehavior. The parameters used to adjust the mathematical model aregenerally dependent on the specific mathematical model used. In the caseof the modified Mohr-Coulomb model, such parameters include the initialdamage parameter, initial values of fracture tensor components, and/orcalibration coefficients for the relation between equivalent stress andstrain rate, for grade dependence, for strain-rate dependence, and thelike.

Block 111 calls for providing a latest mathematical model as a verifiedmathematical model based upon the rock deformation parameter obtainedfrom simulation being with a selected range of the measured rockdeformation parameter. That is, the latest iteration of the model forthe latest run simulation that provides a match is designated as theverified mathematical model. In other words, the digital model can becalled verified if the bulk properties and the bulk behavior arematching. It should be noted that blocks 106-111 are generallyimplemented using a processor.

The method 100 may also include performing an action on the earthformation using a parameter obtained from the verified mathematicalmodel. For example, the verified mathematical model may be used toestimate rock strength parameters of a greater earth formation. Insertedas parameters in a subsurface geomechanical simulation, the rockstrength parameters determine under which operational constraints theearth formation stays intact. From the estimated rock strengthparameters inserted into the model those skilled in the art can optimizethe development of hydrocarbon production by e.g. adjusting hydrocarbonpump rates, hereby avoid damage to the rock which may otherwise producegrains of sand. From the estimated intact rock strength combined withthe in-situ stress the user can calculate the minimum bottom holepressure for solid free production in a so-called sand productionprediction analysis. The sand production prediction analysis uses rockmechanic calculations in combination with an experimental or empiricalderived critical deformation parameter (such as a critical amount ofstrain) to calculate at which bottom hole pressure or reservoir pressurethe wellbore wall will start to fail and grains will be transported inthe produced fluids or gas. By controlling the production rates bychanging valve settings at the well, the user can possibly avoid thesolid production. In another example, the estimated rock strengthparameter is used to determine a mud or drilling fluid weight that wouldavoid a collapse of a borehole being drilled. Based on the rock strengthparameters of the earth formation, those skilled in the art will changethe weight of the drilling fluid by adjusting its density to fall withinsafe operational limits. The weight limits being large enough to avoidthe borehole collapsing upon itself due to the weight and stresses ofthe earth formation surpassing the limits of the rock strength. And theweight limits being small enough to avoid the formation of fractures asan effect of the drilling fluid pressure surpassing the rock strengthparameters of the earth formation.

It can be appreciated that the method 100 providing the verified digitalrock model has several advantages. One advantage is that the verifieddigital rock model has an accurate representation of the rock's micro-and macro properties which capture the effects of micro-cracks anddamage. On the digital sample further forward modeling can be applied torun multiple simulated “destructive” tests with different configurationsto obtain a more complete catalogue of rock properties. In contrast, aphysical sample would only support a single destructive test from whichlimited information can be obtained (e.g. tensile strength, UCS). Thepossibility of repeated destructive tests allows one skilled in the artto obtain additional information, e.g. the rock strength as a functionof confining pressure and/or of changes in temperature. This additionalinformation helps to create a more complete model of material behavior,which is more useful for the application to subsurface conditions thanlimited information (e.g., no confining pressure at room temperature).

Another advantage is that the digital rock model can separate the matrixproperties from the macro-properties. For example, the unconfinedcompressive strength (UCS) from samples without damage is expected tohave higher values as opposed to the samples which have fractures. Underassumption of the matrix properties, a mechanism based material modelcan add any degree and distribution of damage to the sample to forwardmodel the bulk rock properties of differently damaged rocks.

Next, examples of production equipment are discussed. FIG. 4 depictsaspects of production equipment for producing hydrocarbons from an earthformation. A production rig 40 is configured to perform actions relatedto the production of hydrocarbons from the borehole 2 (may also bereferred to as a well or wellbore) penetrating the earth 3 having theearth formation 4. The formation 4 may contain a reservoir ofhydrocarbons that are produced by the production rig 40. The productionrig 40 may include a pump 41 configured to pump hydrocarbons enteringthe borehole 2 to the surface. The pump 41 may include a valve (notshown) for controlling the flow rate of hydrocarbons being pumped. Theborehole 2 may be lined by a casing 45 to prevent the borehole 2 fromcollapsing. The production rig 40 may include a reservoir stimulationsystem 46 configured to stimulate the earth formation 4 to increase theflow of hydrocarbons. In one or more embodiments, the reservoirstimulation system 46 is configured to hydraulically fracture rock inthe formation 4. The production rig 40 may also include a wellrejuvenation system 47 configured to rejuvenate the borehole 2 (e.g.,increase hydrocarbon flow into the borehole 2). In one or moreembodiments, the well rejuvenation system 47 includes an acid treatmentsystem configured to inject acid into the borehole 2.

The production rig 40 may also be configured to extract of core sampleof the formation 4 a downhole coring tool 48. The downhole tool 48 maybe conveyed through the borehole 2 by an armored wireline that alsoprovides communications to the surface. The core sample may be extractedusing an extendable core drill 49. Once the core sample is extracted, itis stored and conveyed to the surface for analysis. In general, aplurality of core samples is extracted in order to adequately representthe properties of rock present in the formation. For example, a highernumber of samples would be required if the properties changesignificantly with depth as opposed to not changing significantly withdepth.

FIG. 4 also illustrates a computer processing system 42. The computerprocessing system 42 is configured to implement the methods disclosedherein. Further, the computer processing system 42 may be configured toact as a controller for controlling operations of the production rig 40to include core sample extraction and analysis. Non-limiting examples ofcontrol actions include turning equipment on or off, setting setpoints,controlling pumping and/or flow rates, and executing processes forformation stimulation and well rejuvenation. In general one or more ofthe control actions may be determined using a formation parameterobtained from the verified model. In one or more embodiments, thecomputer processing system 42 may update or receive an update of theverified model in real time and, thus, estimate the formation parameterand provide control actions in real time.

Next, examples of drilling equipment are discussed. FIG. 5 depictsaspects of drilling equipment. A drill rig 50 is configured to drill theborehole 2 into the earth 3 according to a desired trajectory orgeometry. The drill rig 50 includes a drill string 56 and a drill bit 57disposed at the distal end the drill string 56. The drill rig 50 isconfigured to rotate the drill string 56 and thus the drill bit 57 inorder to drill the borehole 2. In addition, the drill rig 50 isconfigured to pump drilling mud (i.e., drill fluid) of a selected weightthrough the drill string 56 in order to lubricate the drill bit 57 andflush cuttings from the borehole 2. A geo-steering system 55 is coupledto the drill string 56 and is configured to steer the drill bit 57 inorder to drill the borehole 2 according to the desired trajectory. Acontroller 52 is configured to control operations of the drill rig 50 toinclude controlling the geo-steering system 55. In one or moreembodiments, the geo-steering system can control the direction ofdrilling by exerting a force on the borehole wall using extendable pads.The computer processing system 42 may provide inputs into the controller52 based upon formation parameters estimated using the verified model.In one or more embodiments, the computer processing system may receiveupdates of the verified model in real time and, thus, estimate theformation parameter and provide inputs to the controller 52 in realtime.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1

A method for estimating a property of an earth formation, the methodcomprising: obtaining a sample of rock from the earth formation;scanning the sample with a volumetric imaging device to obtain athree-dimensional volume representation of the sample; determininginternal rock damage of the sample using the three-dimensional volumerepresentation of the sample; performing one or more tests on the sampleusing a rock test device; measuring a deformation parameter of thesample using a deformation sensor; constructing a mathematical model ofthe sample that replicates the determined and measured internal rockdamage and damage distribution of the sample; simulating the one or moretests using the mathematical model; obtaining a rock deformationparameter using the one or more simulated tests corresponding to themeasured rock deformation parameter; comparing the rock deformationparameter obtained from the one or more simulated tests to thecorresponding measured rock deformation parameter; adjusting parametersof the mathematical model based upon the rock parameter obtained fromsimulation not being within a selected range of the measured rockparameter; and providing the mathematical model as a verifiedmathematical model based upon the rock parameter obtained fromsimulation being within a selected range of the measured rock parameter;wherein the determining, constructing, obtaining a rock deformationparameter, comparing adjusting, and providing are performed using aprocessor.

Embodiment 2

The method according to any prior embodiment, wherein obtaining a sampleof rock comprises using a downhole coring tool.

Embodiment 3

The method according to any prior embodiment, wherein the testingcomprises at least one of non-destructive testing and destructivetesting.

Embodiment 4

The method according to any prior embodiment, wherein the destructivetesting comprises multistage testing in which successive stages resultin increasing damage.

Embodiment 5

The method according to any prior embodiment, wherein the deformationsensor comprises at least one of a strain sensor, a size measuringsensor, and an acoustic transducer.

Embodiment 6

The method according to any prior embodiment, wherein measuringcomprises determining a location of damage using acoustic signalsobtained from the acoustic transducer.

Embodiment 7

The method according to any prior embodiment, wherein the mathematicalmodel comprises a modified Mohr-Coulomb model having a term representingdilatation in an out-of-plane orientation.

Embodiment 8

The method according to any prior embodiment, further comprisingestimating a parameter of the earth formation using the verifiedmathematical model and performing an action related to the earthformation with action-related equipment using the estimated parameter.

Embodiment 9

The method according to any prior embodiment, wherein the parameter ofthe earth formation is unconfined compressive strength (UCS) of theearth formation and the action is pumping hydrocarbons from the earthformation using a pump at a flow rate determined by the unconfinedcompressive strength (UCS) in order to avoid sand grains from beingpumped with the hydrocarbons.

Embodiment 10

The method according to any prior embodiment, wherein the parameter ofthe earth formation is unconfined compressive strength (UCS) and theaction is pumping drilling fluid for drilling a borehole using drillingequipment, the drilling fluid having a weight that is selected using theunconfined compressive strength (UCS) that avoids collapse of theborehole.

Embodiment 11

The method according to any prior embodiment, wherein the mathematicalmodel comprises a three-dimensional mathematical model.

Embodiment 12

A system for estimating a property of an earth formation, the systemcomprising: a volumetric imaging device configured to scan a sample ofrock form the earth formation to obtain a three-dimensional volumerepresentation of the sample; a rock test device configured to performone or more tests on the sample; a deformation sensor configured tomeasure deformation of the sample due to the one or more tests; a memoryhaving computer-readable instructions; a processor for executing thecomputer-readable instructions, the computer-readable instructionscomprising: determining internal rock damage of the sample using thethree-dimensional volume representation of the sample; constructing amathematical model of the sample that replicates the determined internalrock damage and damage distribution of the sample; simulating the one ormore tests using the mathematical model; obtaining a rock deformationparameter using the one or more simulated tests corresponding to themeasured rock deformation parameter; comparing the rock deformationparameter obtained from the one or more simulated tests to thecorresponding measured rock deformation parameter; adjusting parametersof the mathematical model based upon the rock parameter obtained fromsimulation not being with a selected range of the measured rockparameter; and providing the mathematical model as a verifiedmathematical model based upon the rock parameter obtained fromsimulation being within a selected range of the measured rock parameter.

Embodiment 13

The system according to any prior embodiment, further comprising adownhole coring tool configured to extract a sample of rock from theearth formation.

Embodiment 14

The system according to any prior embodiment, wherein the test equipmentis configured to perform at least one of non-destructive testing anddestructive testing.

Embodiment 15

The system according to any prior embodiment, wherein the deformationsensor comprises at least one of a strain sensor, a size measuringsensor, and an acoustic transducer.

Embodiment 16

The system according to any prior embodiment, wherein the computerreadable instructions further comprise determining a location of damageusing acoustic signals obtained from the acoustic transducer.

Embodiment 17

The system according to any prior embodiment, wherein the mathematicalmodel comprises a modified Mohr-Coulomb model having a term representingdilatation in an out-of-plane orientation.

Embodiment 18

The system according to any prior embodiment, wherein the computerreadable instructions further comprise estimating a parameter of theearth formation using the verified mathematical model and the systemfurther comprises action-related equipment configured to perform anaction using the estimated parameter of the earth formation.

Embodiment 19

The system according to any prior embodiment, wherein the parameter ofthe earth formation is unconfined compressive strength (UCS) of theearth formation and the action is pumping hydrocarbons from the earthformation using a pump at a flow rate determined by the unconfinedcompressive strength (UCS) that avoids sand grains from being pumpedwith the hydrocarbons.

Embodiment 20

The system according to any prior embodiment, wherein the parameter ofthe earth formation is unconfined compressive strength (UCS) and theaction is pumping drilling fluid for drilling a borehole using drillingequipment, the drilling fluid having a weight that is selected using theunconfined compressive strength (UCS) that avoids collapse of theborehole.

In support of the teachings herein, various analysis components may beused including a digital and/or an analog system. For example, thecomputer processing system 42, the controller 52, and/or thegeo-steering system 55 may include digital and/or analog systems. Thesystem may have components such as a processor, storage media, memory,input, output, communications link (wired, wireless, optical or other),user interfaces, software programs, signal processors (digital oranalog) and other such components (such as resistors, capacitors,inductors and others) to provide for operation and analyses of theapparatus and methods disclosed herein in any of several mannerswell-appreciated in the art. It is considered that these teachings maybe, but need not be, implemented in conjunction with a set of computerexecutable instructions stored on a non-transitory computer readablemedium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic(disks, hard drives), or any other type that when executed causes acomputer to implement the method of the present invention. Theseinstructions may provide for equipment operation, control, datacollection and analysis and other functions deemed relevant by a systemdesigner, owner, user or other such personnel, in addition to thefunctions described in this disclosure. Processed data such as a resultof an implemented method may be transmitted as a signal via a processoroutput interface to a signal receiving device. The signal receivingdevice may be a display monitor or printer for presenting the result toa user. Alternatively or in addition, the signal receiving device may bememory or a storage medium. It can be appreciated that storing theresult in memory or the storage medium will transform the memory orstorage medium into a new state (containing the result) from a priorstate (not containing the result). Further, an alert signal may betransmitted from the processor to a user interface if the result exceedsa threshold value.

Further, various other components may be included and called upon forproviding for aspects of the teachings herein. For example, a sensor,transmitter, receiver, transceiver, antenna, controller, optical unit,electrical unit or electromechanical unit may be included in support ofthe various aspects discussed herein or in support of other functionsbeyond this disclosure.

Elements of the embodiments have been introduced with either thearticles “a” or “an.” The articles are intended to mean that there areone or more of the elements. The terms “including” and “having” areintended to be inclusive such that there may be additional elementsother than the elements listed. The conjunction “or” when used with alist of at least two terms is intended to mean any term or combinationof terms. The term “configured” relates one or more structurallimitations of a device that are required for the device to perform thefunction or operation for which the device is configured.

The flow diagram depicted herein is just an example. There may be manyvariations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order, or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While one or more embodiments have been shown and described,modifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustrations and not limitation.

It will be recognized that the various components or technologies mayprovide certain necessary or beneficial functionality or features.Accordingly, these functions and features as may be needed in support ofthe appended claims and variations thereof, are recognized as beinginherently included as a part of the teachings herein and a part of theinvention disclosed.

While the invention has been described with reference to exemplaryembodiments, it will be understood that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the invention. In addition, many modifications will beappreciated to adapt a particular instrument, situation or material tothe teachings of the invention without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for performing an operation on an earthformation using an estimated property of the earth formation, the methodcomprising: obtaining a sample of rock from the earth formation;scanning the sample with a volumetric imaging device to obtain athree-dimensional volume representation of the sample; determininginternal rock damage of the sample using the three-dimensional volumerepresentation of the sample; performing one or more tests on the sampleusing a rock test device; measuring a deformation parameter of thesample using a deformation sensor; constructing a mathematical model ofthe sample that replicates the determined and measured internal rockdamage and damage distribution of the sample; simulating the one or moretests using the mathematical model; obtaining a rock deformationparameter using the one or more simulated tests corresponding to themeasured rock deformation parameter; comparing the rock deformationparameter obtained from the one or more simulated tests to thecorresponding measured rock deformation parameter; adjusting parametersof the mathematical model based upon the rock parameter obtained fromsimulation not being within a selected range of the measured rockparameter; providing the mathematical model as a verified mathematicalmodel based upon the rock parameter obtained from simulation beingwithin a selected range of the measured rock parameter; estimating anunconfined compressive strength (UCS) of the earth formation using theverified mathematical model; and at least one of (a) pumpinghydrocarbons from the earth formation using a pump and a controller at aflow rate determined by the estimated unconfined compressive strength(UCS) in order to avoid sand grains from being pumped with thehydrocarbons, and (b) pumping drilling fluid for drilling a boreholeusing drilling equipment, the drilling fluid having a weight that isselected using the estimated unconfined compressive strength (UCS) toavoid collapse of the borehole; wherein the determining, constructing,obtaining a rock deformation parameter, comparing adjusting, providing,and estimating are performed using a processor.
 2. The method accordingto claim 1, wherein obtaining a sample of rock comprises using adownhole coring tool.
 3. The method according to claim 1, wherein thetesting comprises at least one of non-destructive testing anddestructive testing.
 4. The method according to claim 3, wherein thedestructive testing comprises multistage testing in which successivestages result in increasing damage.
 5. The method according to claim 1,wherein the deformation sensor comprises at least one of a strainsensor, a size measuring sensor, and an acoustic transducer.
 6. Themethod according to claim 1, wherein measuring comprises determining alocation of damage using acoustic signals obtained from the acoustictransducer.
 7. The method according to claim 1, wherein the mathematicalmodel comprises a modified Mohr-Coulomb model having a term representingdilatation in an out-of-plane orientation.
 8. The method according toclaim 1, wherein the mathematical model comprises a three-dimensionalmathematical model.
 9. A system for performing an operation on an earthformation using an estimated property of the earth formation, the systemcomprising: a volumetric imaging device configured to scan a sample ofrock form the earth formation to obtain a three-dimensional volumerepresentation of the sample; a rock test device configured to performone or more tests on the sample; a deformation sensor configured tomeasure deformation of the sample due to the one or more tests; a memoryhaving computer-readable instructions; a processor for executing thecomputer-readable instructions, the computer-readable instructionscomprising: determining internal rock damage of the sample using thethree-dimensional volume representation of the sample; constructing amathematical model of the sample that replicates the determined internalrock damage and damage distribution of the sample; simulating the one ormore tests using the mathematical model; obtaining a rock deformationparameter using the one or more simulated tests corresponding to themeasured rock deformation parameter; comparing the rock deformationparameter obtained from the one or more simulated tests to thecorresponding measured rock deformation parameter; adjusting parametersof the mathematical model based upon the rock parameter obtained fromsimulation not being with a selected range of the measured rockparameter; providing the mathematical model as a verified mathematicalmodel based upon the rock parameter obtained from simulation beingwithin a selected range of the measured rock parameter; and estimatingan unconfined compressive strength (UCS) of the earth formation usingthe verified mathematical model; at least one of (a) a pump andcontroller configured to pump hydrocarbons from the earth formation at aflow rate determined by the estimated unconfined compressive strength(UCS) in order to avoid sand grains from being pumped with thehydrocarbons, and (b) drilling fluid for drilling a borehole usingdrilling equipment, the drilling fluid having a weight that is selectedusing the estimated unconfined compressive strength (UCS) to avoidcollapse of the borehole.
 10. The system according to claim 9, furthercomprising a downhole coring tool configured to extract a sample of rockfrom the earth formation.
 11. The system according to claim 9, whereinthe test equipment is configured to perform at least one ofnon-destructive testing and destructive testing.
 12. The systemaccording to claim 9, wherein the deformation sensor comprises at leastone of a strain sensor, a size measuring sensor, and an acoustictransducer.
 13. The system according to claim 12, wherein the computerreadable instructions further comprise determining a location of damageusing acoustic signals obtained from the acoustic transducer.
 14. Thesystem according to claim 9, wherein the mathematical model comprises amodified Mohr-Coulomb model having a term representing dilatation in anout-of-plane orientation.